In Irish mythology, Hungry Grass (Irish: féar gortach;) also known as Fairy Grass, is a cursed patch of grass. Anyone walking on it was doomed to perpetual and insatiable hunger and a permanent state of weakness.
Harvey suggests that the hungry grass is cursed by the proximity of an unshriven corpse (the fear gorta) or maybe a leprechaun. William Carleton's stories indeed suggest that faeries plant the hungry grass. According to Harvey, this myth may relate to beliefs formed in the Irish Potato Famine of the 1840s, actually caused by fungi. In Margaret McDougall's letters the phrase "Hungry Grass" is - by analogy to the myth - used to describe hunger pains. An alternative version of the hungry grass story relates that anyone walking through it is struck by temporary hunger; to safely cross through one must carry a bit of food to eat along the way (such as a sandwich or several crackers), and some beer.
The Irish Famine
The Irish Famine (or Great Hunger) was a disease that made the Hungry Grass debatable whether or not it was real or just a superstition. People thought the hungry grass just doesn't eat people, it eats crops too. It wasn't always called "Hungry Grass", people thought that a spirit of a man was, in fact, eating people. The word "fear" in Irish is both "man and grass" so, Hungry Man came to be because they feared him. It was said that if you give relief to Hungry Man, you will enjoy unfailing prosperity, even during the worst periods of famine and death. Nobody knew what the "Hungry Man" looked liked but visitations to Ireland may have given him an appearance. After this, Maxwell who wrote "Wild Sports of the West" made a assumption and called this Famine "Hungry Disease", that was made by fairies or was grown over by a corpse. Hungry Grass was eventually what it was really called, because certain grass you stepped on made you faint and kill over, this happened to many farmers and fishermen.
Some have said that Hungry Hill is where Hungry Grass has originated from. The first person that ventured on the hill were never seen again. People were afraid to even go by the hill. Never the less, someone else eventually got to go up on the hill and lived. A young fisherman that came to Ireland wanted to fish there, and the ocean was behind Hungry Hill. So, in the morning, the fisherman forgot to eat breakfast so he thought he would eat it on the way to the ocean, He brought an apple and sandwich for lunch. He got the apple out and started eating it.
As he got to the hill, people started yelling not to go upon the hill but, he didn't listen. As he was climbing, the grass on the hill wiggled almost snake like, and wrapped around him. He was still eating and every time he took a bite it would fall off of him. When he got to shore, other fishermen told him that the hill was said to kill people. He then put two and two together and came to the conclusion, that if you ate while on the grass you wouldn't fall ill.
The fairies were furious and desisted to plant Hungry Grass everywhere. Some people brought food with them where ever they went, others were skeptic and eventually fell to their doom. The famine had eventually stopped when people built a wall around Hungry Hill. If the wall was to ever fail the hungry grass may come back again.